The present invention relates to a mechanism for adjusting the position of a pickup used in a player for reproducing information recorded in a disc such as a digital audio disc (CD) and a laser video disc (LD). In order to precisely reproduce the information recorded in a disc with a player, it is necessary to precisely determine the inclination of a pickup in both a tracking direction and a tangential direction and to control the pickup by means of a servo mechanism. Further, it is necessary that the center of a pickup, that is, the optical axis of an objective lens, be aligned with a plane which extends in the axial direction of a turntable and which includes a path extending in the radial direction of the turntable disposed parallel to the straight line movement of a slider which supports the pickup.
FIG. 9 is a perspective view of a conventional mechanism for adjusting the inclination of a pickup of a player, and FIG. 10 is an exploded perspective view of the mechanism of FIG. 9.
In FIGS. 9 and 10, a spindle motor 1 is mounted on a chassis (not shown), and a turntable 2 is mounted on a rotatable spindle of the spindle motor 1. A disc is adapted to be placed on the turntable 2.
A slider 3 is driven by a linear motor (not shown) for movement in the radial direction of the turntable 2, that is, in an X-axis direction, along guide bars (not shown). The slider includes a bottom wall 3a, a block 3b mounted on one side edge portion of the bottom wall 3a and extending in a direction of a Y-axis perpendicular to the X-axis, and first through third side walls 3c-3e formed respectively on three sides of the bottom wall 3a.
The bottom wall 3a has a threaded hole 3a in which a threaded portion of a first adjustment screw 10 (described later) is threaded. The block 3b has a hole 3b.sub.1 in which a pivot pin 6, mounted on a lever 4 (described later), is angularly movably received, a recess 3b.sub.2 in which part of a round rod 8 (described later) and a first spring 9 are received, and threaded holes 3b.sub.3 and 3b.sub.4 in which a second adjustment screw 14 (described later) and a screw 13 for mounting a second leaf spring 12 are respectively threaded.
The first side wall 3c disposed in opposed relation to the block 3b has a recess 3c.sub.1 into which one end of the round rod 8 is urged to be received, and a projection 3c.sub.2 which holds a pickup 7 (described later) apart from the first side wall 3c by a predetermined distance.
A straight line interconnecting the center of the recess 3b.sub.2, formed in the block 3b, and the center of the recess 3c.sub.1, formed in the first side wall 3c, is substantially parallel to the X-axis.
The lever 4 includes a first flat portion 4a having an abutment portion 4a.sub.1 abutting against the lower surface of the pickup 7, a vertical portion 4b extending from the first flat portion 4a, and a second flat portion 4c formed at one end of the vertical portion 4b on the side opposite to the first flat portion 4a. The second flat portion 4c has a hole 4c.sub.1 through which the threaded portion of the first adjustment screw 10 passes, with the head of the screw held against the second flat portion 4c.
A first leaf spring 5 is mounted on the first flat portion 4a of the lever 4, and has a first spring portion 5a for upwardly urging the lower surface of the pickup 7 at the side opposite to the abutment portion 4a.sub.1 of the lever 4, and a second spring portion 5b for urging the pickup 7 toward the first side wall 3c of the slider 3.
The pivot pin 6 is mounted on the outer surface of the vertical portion 4b of the lever 4, and is angularly movably received in the hole 3b.sub.1 formed through the block 3b of the slider 3.
An objective lens 7a, which is driven for movement in the upward and downward directions, is mounted on the upper side of the pickup 7, and the pickup 7 has a hole 7b formed therethrough and extending in the X-axis direction. The round rod 8 is angularly movably received in the hole 7b.
Therefore, the optical axis of the objective lens 7a is offset from the center line of the hole 7b by an amount of y.sub.0 in the Y-axis direction.
The round rod 8 is conical at one end thereof, and extends through the hole 7b in the pickup 7 and is received at the one end thereof in the recess 3c.sub.1 in the first side wall 3c of the slider 3. The other end of the round rod 8 is received in the recess 3b.sub.2 in the block 3b, and the round rod 8 is pivotally movable about the one end thereof received in the recess 3c.sub.1.
Therefore, the optical axis of the objective lens 7a of the pickup 7 is offset from the center of pivotal movement of the round rod 8 by an amount of x.sub.0 in the X-axis direction.
The first spring 9 is provided in the recess 3b.sub.2 formed in the block 3b of the slider 3, and urges the other end of the round rod 8 upwardly.
The first adjustment screw 10 serves to adjust the inclination of the pickup 7 in the tangential direction. The head of this screw abuts against the second flat portion 4c of the lever 4, and its threaded portion passes through the hole 4c.sub.1 of the second flat portion 4c and a second spring 11 and is threaded into the threaded hole 3a.sub.1 formed in the bottom wall 3a of the slider 3. The second spring 11 urges the second flat portion 4c upwardly.
The second leaf spring 12 is mounted to the block 3b of the slider 3 by the screw 13, and includes a first spring portion 12a for urging the other end of the round rod 8 downwardly, and a second spring portion 12b for urging the round rod 8 toward the first side wall 3c of the slider 3.
Formed through the first portion 12a is a slot 12a.sub.1 through which the threaded portion of the second adjustment screw 14 extends.
The second adjustment screw 14 serves to adjust the inclination of the pickup 7 in the tracking direction. Its head is held against the first spring portion 12a of the second leaf spring 12, and its threaded portion passes through the slot 12a.sub.1 of the second leaf spring 12 and is threaded into the threaded hole 3b.sub.3 formed in the block 3b of the slider 3.
The operation will now be described.
First, when the inclination of the pickup 7 in the tracking direction is to be adjusted, the second adjustment screw 14 is angularly moved, so that the round rod 8 is pivotally moved about the recess 3c.sub.1 formed in the first side wall 3c of the slider 3. Therefore, the inclination of the pickup 7 in the tracking direction can be adjusted by adjusting the second adjustment screw 14.
When the inclination of the pickup 7 in the tangential direction is to be adjusted, the first adjustment screw 10 is angularly moved to angularly move the lever 4 about the pivot pin 6. At this time, because of the provision of the round rod 8, the pickup 7 is angularly moved about the round rod 8. Therefore, the inclination of the pickup 7 in the tangential direction can be adjusted by adjusting the first adjustment screw 10.
In the conventional mechanism for adjusting the inclination of a pickup having the above construction, when the inclination of the pickup 7 in the tracking direction is to be adjusted, the pickup 7 is angularly moved about the portion of the round rod 8 held against the first side wall 3c. When the inclination of the pickup 7 in the tangential direction is to be adjusted, the pickup 7 is angularly moved about the round rod 8.
Therefore, the origin of adjustment of the inclination of the pickup 7 in the tracking and tangential directions is the portion of the round rod 8 held against the first side wall 3c.
The portion of the round rod 8 held against the first side wall 3c is offset from the optical axis of the objective lens 7a of the pickup 7 by an amount of x.sub.0 in the X-axis direction and also by an amount of y.sub.0 in the Y-axis direction. Therefore, when at least one of the inclinations of the pickup 7 in the tracking and tangential directions is adjusted, the height of the pickup 7 is changed. It is cumbersome to adjust the inclination of the pickup 7 in the tracking and/or tangential directions while suitably adjusting the height of the pickup, and this is disadvantageous in that much time is required for the adjustment operation.
Further, in the conventional device, when the centering of the pickup is to be adjusted, a slider drive mechanism for driving the slider is fixed to a chassis. Thus, in this condition a spindle motor to which the turntable is mounted is provisionally fixed to the chassis, and when the path of the optical axis of the objective lens of the pickup is brought into alignment with the radial direction of the turntable, a mounting screw is tightened to finally fix the spindle motor to the chassis.
Conventionally, the centering of the pickup of a player has been carried out in the above-described manner, and therefore when the spindle motor is to be finally fixed to the chassis by tightening the mounting screw, the spindle motor is displaced with respect to the chassis, so that the center of the pickup is shifted.
Therefore, disadvantages are encountered in that the centering of the pickup is cumbersome and a lot of time is required for the adjustment operation.